Patients with Adult and Juvenile Rheumatoid Arthritis will be typed for twelve HLA-D specificities including HLA-DW1, DW2, DW3, DW4, DW5, DW6, LD-107, LD-108, LD-TMo, LD-BCo and LD-WF1. Patients and control subjects of Caucasian, Black-American and Mexican-American origin will be studied separately. Particular attention will be given to the clinical varieties of rheumatoid arthritis to define markers for immunogenetic factor operative in different forms of the disease as well as associated or related conditions. BIBLIOGRAPHIC REFERENCES: Stastny, P. HLA-D typing in rheumatoid arthritis. Arthritis Rheum. 20:000, 1977. Stastny, P. Typing by compatibility in mixed lymphocyte culture using LD homozygous typing cells. Transpl. Proc. 9:000, 1977.